Battery Case

This is the U.S. National Phase application of PCT/JP2024/015417, filed Apr. 18, 2024 which claims priority to Japanese Patent Application No. 2023-072578, filed Apr. 26, 2023, the disclosures of these applications being incorporated herein by reference in their entireties for all purposes.

The present disclosure relates to a battery case.

An electric vehicle mounted with a motor for traveling is mounted with a battery, which supplies electric power to the motor, in a state in which the battery is housed in a battery case. When the capacity of the battery is increased in order to increase a cruising distance of the electric vehicle, the size of the battery case increases accordingly. Thus, in order to ensure a wide vehicle interior, many electric vehicles mounted with battery cases below floor panels of vehicle body structures.

An electric vehicle includes a vehicle body component and a structure for protecting a battery at the time of collision or the like and is configured to be able to protect the battery at the time of deformation of a vehicle body due to collision.

For example, Patent Literature 1 discloses, in an electric vehicle mounted with a battery case including a bathtub-shaped tray that houses the battery, a structure in which a frame is disposed so as to surround front, rear, left, and right of the tray as a vehicle body component for protecting a battery at the time of collision.

Patent Literature 2 discloses a battery case lower tray including a plurality of reinforcements and a plurality of reinforcing members that couple the reinforcements adjacent to one another. In the configuration described in Patent Literature 2, when a pressing force acts on regions among the reinforcements adjacent to one another, the pressing force is dispersed and transmitted to the plurality of reinforcements via the reinforcing members. Therefore, the pressing force transmitted to one reinforcement is reduced. Accordingly, since the reinforcements are less easily buckled and deformed, deformation of a tray main body can be suppressed.

Patent Literature 3 discloses a frame-shaped frame disposed to surround front, rear, left, and right of a battery. The frame-shaped frame includes a pair of longitudinal ribs extending in the vehicle front-rear direction and a cross member supported by the pair of longitudinal ribs and extending in the vehicle width direction. The cross member includes a first plate member and a second plate member that are disposed to face each other in the vehicle front-rear direction and joined to each other. The length in the vehicle width direction of the cross member can be adjusted by adjusting an amount of overlap in the vehicle width direction between the first plate member and the second plate member and joining the first plate member and the second plate member.

Patent Literature 4 discloses a beam assembly that can be used as a component of a battery tray. The beam assembly has structure in which a plurality of elongated beams are joined. The elongated beam includes an elongated tubular portion and a protruding portion protruding from the tubular portion to the outer side and has a P-shaped cross section. The beam assembly is configured by a first beam and a second beam cut from a single elongated beam. The beam assembly has structure in which the first and second beams are aligned in parallel and rotated approximately 180 degrees axially along the longitudinal direction to attach one protruding portion to the other tubular portion.

Patent Literature 5 discloses a battery case support structure that supports and protects a battery case with a vehicle frame member. A vehicle frame member includes a pair of side frames disposed on the vehicle width direction outer side of the battery case and a cross member disposed below the battery case and has structure in which the side frames and the cross member are integrated. The side frame is substantially B-shaped in a cross sectional shape orthogonal to an extending direction. The side frame includes one vertical wall portion and two protrusions protruding to the vehicle width direction inner side from the vertical wall portion and is configured by one member.

Patent Literature 1: JP 2021 041783 A Patent Literature 2: JP 2020 053132 A Patent Literature 3: JP 2023 016511 A Patent Literature 4: JP 2023-515495 W Patent Literature 5: JP 2020-125023 A

In the configuration described in Patent Literature 1, since the frame-shaped frame is disposed to surround the entire periphery of the tray, strength can be ensured but many frame members are necessary. For that reason, an area in which the battery can be housed is limited with respect to the surface area of the tray. Since the frame is made of metal, weight increases by the weight of the frame and energy efficiency decreases.

In the configuration described in Patent Literature 2, it is possible to prevent deformation of the tray main body without any problem in strength if the tray main body is made of metal. However, an increase in weight is significant when the tray main body is made of iron and, if light metal is used for a reduction in weight, cost increases. When the tray main body is made of resin, a reduction in weight is possible but, on the other hand, since strength is low, it is necessary to increase resin thickness or reinforce the tray main body to prevent deformation of the tray main body. There is a problem of an increase in weight and an increase in manufacturing cost.

In the configuration described in Patent Literature 3, since each of the first plate member and the second plate member configuring the cross member is disposed to be supported by only one of the pair of longitudinal ribs, there is a problem that the rigidity of the cross member against a collision load from the vehicle width direction is low and deformation (bending deformation) easily occurs in the cross member. Although a configuration in which both end portions of the cross member, which are non-overlapping portions between the first plate member and the second plate member, and the center of the cross member are reinforced against the deformation of the cross member is disclosed, the configuration is insufficient to improve load-bearing performance against a load acting in the vehicle width direction at the time of side surface collision.

5 Patent Literature 4 only discloses the beamassembly. If the beam assembly is joined as a component of the battery tray in a poor manner, the beam assembly is likely to be unable to exert predetermined performance.

Patent Literature 5 discloses the structure in which, for the vehicle frame member in which the pair of side frames are connected by the cross members, the battery case is only placed and fixed on the upper surface of the vehicle frame member and is not a structure where collision characteristics are improved by the battery case and the vehicle frame. For that reason, when an impact from a side is received, the substantially B-shaped cross-sectional shape of the side frame easily collapses and is bent and deformed and the deformed side frame intrudes into the inner side of the battery case. Therefore, the vehicle frame member cannot have sufficient load-bearing performance.

The present disclosure has been made in order to solve the problems described above, and an object of the present disclosure is to provide a battery case having sufficient rigidity and strength without requiring a significant increase in weight and manufacturing cost.

According to the present disclosure, a battery case that is mounted below a floor of a vehicle body and houses a battery, includes: a main body including a bottomed frame body including a pair of side wall portions facing each other in a vehicle width direction in a state of being mounted on the vehicle body; an inner cross member extending in the vehicle width direction to extend over the pair of side wall portions in the main body to reinforce the main body; and a side frame that extends in a vehicle front-rear direction outside the main body and is joined to outer surfaces of the pair of side wall portions to reinforce the main body. Further, the inner cross member includes: a top plate section; a pair of vertical wall portions formed in series from the top plate section via an upper bent section; and a pair of flange sections formed in series from the vertical wall portion via a lower bent section, the pair of vertical wall portions includes: a front side vertical wall portion formed continuously from the top plate section to a front side in the vehicle front-rear direction; and a rear side vertical wall portion that faces the front side vertical wall portion in the vehicle front-rear direction and is formed continuously from the top plate section to a rear side in the vehicle front-rear direction, and a ridgeline portion extending in the vehicle width direction is formed in at least one of the front side vertical wall portion and the rear side vertical wall portion.

In the battery case according to the present disclosure, the ridgeline portion is formed over an entire length in a longitudinal direction of the inner cross member.

In the battery case according to the present disclosure, in at least one of the front side vertical wall portion and the rear side vertical wall portion, a recess recessed toward another vertical wall facing the one vertical wall portion, and the recess is formed to include a plurality of the ridgeline portions and extends in the vehicle width direction.

In the battery case according to the present disclosure, the recess includes: a front side recess formed in the front side vertical wall portion; a rear side recess formed in the rear side vertical wall portion, and the front side recess and the rear side recess are joined in portions facing each other in the vehicle front-rear direction.

In the battery case according to the present disclosure, the flange section is joined to a bottom of the main body.

In the battery case according to the present disclosure, the inner cross member is joined in a state in which an end portion in the vehicle width direction is in contact along the side wall portion.

In the battery case according to the present disclosure, in the inner cross member, both of the front side vertical wall portion and the rear side vertical wall portion are connected to the side wall portion.

The battery case according to the present disclosure includes a center frame that extends in the vehicle front-rear direction in the main body and is provided to extend over a front wall portion and a rear wall portion of the main body and divides an inside of the main body in the vehicle width direction. Further, one end portion in the vehicle width direction of the inner cross member is joined to the side wall portion and another end portion in the vehicle width direction of the inner cross member is joined to the center frame.

In the battery case according to the present disclosure, the side frame is a structure made of steel in which a steel sheet is mountain folded and/or valley folded and has a plurality of cross sections extending in the vehicle width direction, and a mountain folded portion and/or a valley folded portion in the side frame forms a plurality of bent portions extending in the vehicle front-rear direction.

In the battery case according to the present disclosure, the side frame includes a side surface portion provided continuously to the cross section via the bent portion, and the side surface portion is a portion joined to an outer surface of the side wall portion.

In the battery case according to the present disclosure, an interval between the cross sections in a vehicle height direction is equal to or smaller than half of a depth of a bottom of the main body.

In the battery case according to the present disclosure, the side frame includes: a first member having a W-shaped cross section spreading toward an outer side or an inner side in the vehicle width direction; and a second member having a flat shape joined to the outer side or the inner side in the vehicle width direction of the first member, and a joining portion of the first member and the second member is joined in a butted state.

In the battery case according to the present disclosure, the side frame includes: a first member having a hat cross-sectional shape spreading toward an inside in the vehicle width direction; and a second member having a U-shaped cross section joined to an outer side in the vehicle width direction of the first member, and a relationship between a curvature radius R of a punch shoulder R portion of the second member and a plate thickness t of the second member satisfies R/t≤3.0.

In the battery case according to the present disclosure, the side frame is configured by a structure having a figure eight-shaped cross section in which two rectangles are overlapped in a vehicle height direction.

In the battery case according to the present disclosure, an uneven shape is formed at a mounting portion of the battery in a bottom of the main body.

The battery case according to the present disclosure, includes a plate member that closes an opening in a vehicle height direction of the uneven shape. Further, a space segmented by the uneven shape and the plate member is used as a flow path for a coolant for cooling the battery.

In the battery case according to the present disclosure, the inner cross member is made of a steel sheet having a yield strength of 500 MPa class or more, and the side frame is made of a steel sheet having tensile strength of 1180 MPa class or more.

According to the present disclosure, it is possible to achieve a structure of a battery case having rigidity and strength higher than those in the related art without requiring a significant increase in weight and manufacturing cost.

Hereinafter, a battery case in an embodiment of the present disclosure is specifically explained with reference to the drawings. Note that constituent elements in the embodiment explained below include those that can be easily replaced by those skilled in the art or those that are substantially the same.

1 FIG. 1 2 3 2 4 2 is an exploded diagram for explaining an overall configuration of the battery case in the embodiment. A battery caseincludes a main bodythat houses a battery, an inner cross memberdisposed on the inside of the main body, and a side framedisposed on the outside of the main body.

1 2 1 1 1 1 1 1 The battery caseis mounted on an electric vehicle in a state in which the battery is housed on the inside of the main body. The electric vehicle is a vehicle mounted with a motor for traveling and is, for example, a vehicle such as an electric automobile or a hybrid vehicle. The electric vehicle mounted with the battery caseincludes the motor for traveling and the battery housed in the battery caseand travels by driving the motor by supplying electric power stored in the battery to the motor. The motor is a motor generator capable of functioning as an electric motor and a generator. The battery is configured by a secondary battery such as a lithium ion battery. The battery in the battery caseand the motor for traveling are electrically connected. The battery housed in the battery caseis a battery module including a plurality of battery cells. A plurality of battery modules are housed on the inside of the battery case. That is, the battery caseis a case portion of a battery pack.

1 In this explanation, structure and disposition are explained using a direction in a state in which the battery caseis mounted on the electric vehicle. A front side and a rear side are described as expressions indicating the front and the rear in the vehicle front-rear direction. The left side and the right side are described as expressions indicating the left and the right in the vehicle width direction. The left side in the case in which the electric vehicle is viewed from the rear side to the front side is the vehicle width direction left side and the right side in that case is the vehicle width direction right side. The vehicle width direction is sometimes explained using the inner side and the outer side. The upper side and the lower side are described as expressions indicating upward and downward in the vehicle height direction.

2 10 11 10 2 10 11 2 2 10 11 The main bodyincludes a trayformed by a bottomed frame body and a coverthat closes an upper opening of the tray. An internal space of the main bodyformed by the trayand the coverconfigures a housing chamber that houses the battery. The battery provided in the electric vehicle is mounted on a vehicle body in a state of being housed on the inside of the main body. The main bodyis a structure in which the trayand the coverare integrated.

10 12 13 14 15 16 10 12 13 14 15 16 12 13 14 15 16 10 The trayincludes a pair of side wall portionsandfacing each other in the vehicle width direction in a state of being mounted on the vehicle body, a front wall portionand a rear wall portionfacing each other in the vehicle front-rear direction, and a bottomformed in a quadrangular shape. The trayhas structure in which the side wall portionsand, the front wall portion, the rear wall portion, and the bottomare integrally formed. The side wall portionon the left side, the side wall portionon the right side, the front wall portion, and the rear wall portionstand upward in the vehicle height direction from the peripheral edge of the bottom. The trayneeds to have depth capable of housing the battery and is, for example, a steel structure manufactured by deep drawing in which a steel sheet having tensile strength of 440 MPa class or less is used.

10 11 12 13 14 15 10 An upper portion of the trayis a portion to which the coveris attached and is formed by an upper portion of the side wall portion, an upper portion of the side wall portion, an upper portion of the front wall portion, and an upper portion of the rear wall portion. The upper portion of the trayis formed in a rectangular frame shape.

11 10 11 10 10 The coveris a lid that covers the upper opening of the tray. The coveris attached to the upper portion of the trayby, for example, bolt fastening to close the upper opening of the tray.

10 11 3 4 2 3 4 2 2 1 2 3 4 2 In a state in which the trayand the coverare integrated, the inner cross memberand the side frameare integrated with the main body. The inner cross memberand the side frameare reinforcing members that reinforce the main body. The reinforcing members are also stiffening members that stiffen the main body. The battery caseis formed into a structure that increases the rigidity of the main bodyby the inner cross memberand the side frameintegrated with the main body.

3 2 2 10 3 2 12 13 3 2 2 2 10 3 3 The inner cross memberis provided on the inside of the main bodyand is integrated with the main bodyto reinforce the tray. The inner cross memberis provided in the main bodyto extend over a pair of side wall portionsandfacing each other in the vehicle width direction. The inner cross memberis a member that extends in the vehicle width direction in the main bodyand receives a load in the vehicle width direction input to the main bodyfrom the outside of the main bodyand acting on the tray. Since the inner cross memberextends in the vehicle width direction, the longitudinal direction of the inner cross memberis the same direction as the vehicle width direction.

1 3 3 10 3 12 13 1 FIG. The battery caseincludes a plurality of inner cross membersdisposed at predetermined intervals in the vehicle front-rear direction. As illustrated in, four inner cross membersdisposed at equal intervals in the vehicle front-rear direction are provided on the inside of the tray. Each of the four inner cross membersis configured to extend in the vehicle width direction and extend over the side wall portionon the left side and the side wall portionof the right side.

4 2 2 10 4 2 20 20 2 4 2 20 21 22 23 2 FIG. 1 FIG. The side frameis provided on the outside of the main bodyand is integrated with the main bodyto reinforce the tray. As illustrated in, the side frameis integrated with the main bodyvia a fixing member. The fixing memberis a member that fixes the main bodyto the vehicle body and is a member that fixes the side frameto the main body. As illustrated in, the fixing memberhas structure in which a first fixing member, a second fixing member, and a third fixing memberare integrated and extends in the vehicle front-rear direction.

4 2 12 13 4 10 1 4 12 4 13 The side frameextends in the vehicle front-rear direction outside the main bodyand faces the outer surfaces of the side wall portionsandin the vehicle width direction. The side frameincludes two side frames disposed to sandwich the trayfrom the vehicle width direction both sides. The battery caseincludes the side frameon the left side facing the outer surface of the side wall portionin the vehicle width direction and the side frameon the right side facing the outer surface of the side wall portion.

4 12 13 4 12 4 13 4 12 13 10 2 10 2 The side frameis formed longer than the vehicle front-rear direction length of the side wall portionsand. The side frameon the left side is configured to face, in the vehicle width direction, the entire outer surface of the side wall portionin the vehicle front-rear direction. The side frameon the right side is configured to face, in the vehicle width direction, the entire outer surface of the side wall portionin the vehicle front-rear direction. The side frameis a member that extends in the vehicle front-rear direction at a position facing the side wall portionsandof the trayin the vehicle width direction outside the main bodyand receives a load in the vehicle width direction input to the trayfrom the outside of the main body.

3 FIG. 4 FIG. 3 FIG. 3 is a perspective view for explaining the structure of the inner cross member.is a diagram illustrating the inner cross member as viewed from the vehicle width direction. In, only one side end portion in the longitudinal direction of the inner cross memberis illustrated.

3 31 32 33 34 35 36 The inner cross memberincludes a top plate section, a vertical wall portion, a flange section, an upper bent section, a lower bent section, and a recess.

31 3 31 The top plate sectionis a portion forming the apex of the inner cross member. The top plate sectionhas a cross-sectional shape extending in the vehicle front-rear direction in a cross section orthogonal to the vehicle width direction.

32 3 32 31 33 32 31 34 33 35 34 35 32 32 32 32 32 32 31 31 32 32 32 32 The vertical wall portionis a portion forming a wall portion of the inner cross member. The vertical wall portionforms a portion between the top plate sectionand the flange section. The vertical wall portionis formed in series with the top plate sectionvia the upper bent sectionand is formed in series with the flange sectionvia the lower bent section. A portion between the upper bent sectionand the lower bent sectionis the vertical wall portion. The vertical wall portionis configured by a pair of wall portions facing each other in the vehicle front-rear direction. The vertical wall portionincludes the vertical wall portionon the front side formed on the front side in the vehicle front-rear direction and the vertical wall portionon the rear side formed on the rear side in the vehicle front-rear direction. The vertical wall portionincludes a front vertical wall portion continuously formed on the front side in the vehicle front-rear direction from the top plate sectionand a rear vertical wall portion continuously formed on the rear side in the vehicle front-rear direction from the top plate section. The front vertical wall portion and the rear vertical wall portion face each other in the vehicle front-rear direction. In the following explanation, the “vertical wall portionof the front side formed on the front side in the vehicle front-rear direction” is sometimes simply described as “vertical wall portionon the front side” and the “vertical wall portionon the rear side formed on the rear side” is sometimes simply described as “vertical wall portionon the rear side”.

32 36 36 32 32 36 36 3 32 36 31 36 33 36 In the vertical wall portion, the recessincluding a plurality of ridgeline portions extending in the vehicle width direction is provided. The recesshas a shape in which a part of the vertical wall portionis recessed to the other vertical wall portionside. The recessextends in the vehicle width direction. The recessis formed over the entire length in the longitudinal direction of the inner cross member. The vertical wall portionincludes a portion where the recessis formed, a portion further on the top plate sectionside than the recess, and a portion further on the flange sectionside than the recess.

36 41 42 43 44 32 41 42 43 44 The recessis formed by a first ridgeline portion, a second ridgeline portion, a third ridgeline portion, and a fourth ridgeline portion. In the vertical wall portion, the first ridgeline portion, the second ridgeline portion, the third ridgeline portion, and the fourth ridgeline portionare provided.

3 FIG. 4 FIG. 41 42 43 44 41 42 43 44 3 41 42 43 44 41 42 43 44 As illustrated in, the ridgeline portions,,, andextend in the vehicle width direction. The ridgeline portions,,, andare formed over the entire length in the longitudinal direction of the inner cross member. As illustrated in, the first ridgeline portion, the second ridgeline portion, the third ridgeline portion, and the fourth ridgeline portionare provided at different positions in the vehicle height direction. The first ridgeline portion, the second ridgeline portion, the third ridgeline portion, and the fourth ridgeline portionare provided in this order from the upper side in the vehicle height direction.

41 32 32 42 32 43 32 32 44 32 The first ridgeline portionis, in the vertical wall portion, a boundary portion between an upper portion extending in the vehicle height direction and an upper inclined portion extending to be inclined with respect to the vehicle height direction to approach the other vertical wall portion. The second ridgeline portionis, in the vertical wall portion, a boundary portion between the upper inclined portion and an intermediate portion extending in the vehicle height direction. The third ridgeline portionis, in the vertical wall portion, a boundary portion between the intermediate portion and a lower inclined portion extending to be inclined with respect to the vehicle height direction to be separated from the other vertical wall portion. The fourth ridgeline portionis, in the vertical wall portion, a boundary portion between the lower inclined portion and a lower portion extending in the vehicle height direction.

32 32 32 32 34 35 3 3 32 3 3 As explained above, a plurality of ridgeline portions are formed in the vertical wall portion. The vertical wall portionhas structure bent in a convex shape to one side and/or the other side in the out-of-plane direction of the vertical wall portion. For that reason, the vertical wall portionhas a portion extending in the vehicle height direction, a portion inclined with respect to the vehicle height direction, and a bent section as a cross-sectional shape orthogonal to the vehicle width direction. In addition to the ridgelines extending in the longitudinal direction (the vehicle width direction) formed in the upper bent sectionand the lower bent sectionof the inner cross member, the plurality of ridgeline portions extending in the longitudinal direction (the vehicle width direction) over the entire length in the longitudinal direction of the inner cross memberis also formed in the vertical wall portionof the inner cross member. Accordingly, rigidity (proof stress) against a load (a side collision load) input in the longitudinal direction (the vehicle width direction) from the end portion of the inner cross membercan be improved.

3 36 32 3 3 32 3 32 32 3 In order to improve buckling strength against the load input in the longitudinal direction from the end portion of the inner cross member, the ridgeline portion (including the recess) formed in the vertical wall portionof the inner cross memberneeds to continuously extend in the longitudinal direction over the entire length in the longitudinal direction of the inner cross member. When a partial ridgeline portion in the longitudinal direction is provided in the vertical wall portionof the inner cross member, the vertical wall portionincludes a part where a ridgeline portion is not provided at any position in the longitudinal direction. For that reason, in this case, at the time of side surface collision of the electric vehicle, deformation concentrates on a part where no ridgeline portion is provided and the buckling strength is relatively low in the vertical wall portionand the buckling strength of the entire inner cross membercannot be improved.

3 3 36 32 3 4 FIG. 36 FIG. A CAE analysis was performed in order to check this point. The inner cross membersset as a target of the CAE analysis are four types of inner cross membersin which the position in the longitudinal direction forming the ridgeline portion (the recess) of the vertical wall portionillustrated inis changed as illustrated in. Note that types a, b, c, and d are described as inner cross memberswhen not being particularly distinguished.

3 36 32 a 4 FIG. In an inner cross member-of the type a, the ridgeline portion (the recess) of the vertical wall portionillustrated inis formed over the entire length in the longitudinal direction.

3 36 32 3 b b. 4 FIG. In an inner cross member-of the type b, the ridgeline portion (the recess) of the vertical wall portionillustrated inis formed at the center in the longitudinal direction by length of 15% with respect to the overall length in the longitudinal direction of the inner cross member-

3 36 32 3 c c. 4 FIG. In an inner cross member-of the type c, the ridgeline portions (the recesses) of the vertical wall portionillustrated inare formed at both ends in the longitudinal direction by length of 8% with respect to the overall length in the longitudinal direction of the inner cross member-

3 36 32 d 17 FIG. An inner cross member-of the type d is formed in a hat cross-sectional shape and the ridgeline portion (the recess) is not provided in the vertical wall portion(see a type A illustrated in).

18 FIG. 3 3 3 For the structures of the types a to d, as illustrated in, the CAE analysis was performed in which one end of one side of the inner cross memberwas fixed and a load in the longitudinal direction (the vehicle width direction) was applied to the other end to deform the inner cross memberby 3 mm. This load is an axis direction load acting in the longitudinal direction of the inner cross member.

37 FIG. 3 is a diagram illustrating a correspondence relationship between a maximum load (proof stress) of a load-stroke curve obtained by the CAE analysis of the inner cross member and the types of the inner cross member. The maximum load of the load-stroke curve is a load (proof stress) with which the inner cross memberstarts buckling deformation at the time of changing to plastic deformation through elastic deformation immediately after starting deformation and indicates proof stress against side surface collision. As the maximum load (proof stress) is higher, plastic deformation at the time of collision less easily occurs and collision characteristics are better.

37 FIG. 36 3 36 36 As illustrated in, when the ridgeline portions (the recesses) are partially formed at the center (the type b) or both the end portions (the type c) in the longitudinal direction, the maximum load (proof stress) of the inner cross memberis increased by 2% and 6%, respectively, with respect to the load (the proof stress) of type d. On the other hand, in the type a in which the ridgeline portion (the recess) is formed over the entire length in the longitudinal direction, the maximum load (proof stress) is 126% higher with respect to the load (the proof stress) of the type d. The buckling strength can be significantly improved compared with the type b and the type c in which the ridgeline portion (the recess) is partially formed in the longitudinal direction.

33 3 33 32 33 33 32 33 32 The flange sectionis a portion forming the bottom of the inner cross memberand has a cross-sectional shape extending in the vehicle front-rear direction in the cross section orthogonal to the vehicle width direction. The flange sectionis configured by a pair of flange sections extending to the outer side in the vehicle front-rear direction from the pair of vertical wall portions. The flange sectionincludes the flange sectionon the front side protruding from the vertical wall portionon the front side toward the front side in the vehicle front-rear direction and the flange sectionon the rear side protruding from the vertical wall portionon the rear side toward the rear side in the vehicle front-rear direction.

33 16 10 33 16 10 70 70 33 16 10 3 16 10 3 3 5 FIG. The flange sectionis attached to the bottomof the tray. As illustrated in, the flange sectionis joined to the bottomof the trayby a welded portion. The welded portionis a welded portion that joins the flange sectionand the bottomof the trayand is formed by, for example, spot welding. The inner cross memberand the bottomof the trayform a closed cross-sectional structure, whereby the proof stress can be increased. Accordingly, at the time of the side surface collision of the electric vehicle, cross section collapse of the inner cross memberdue to an axis direction load less easily occurs and buckling of the inner cross membercan be suppressed.

6 FIG. 6 FIG. 3 12 13 10 17 3 12 13 17 32 32 32 12 13 3 17 17 17 3 12 17 3 13 3 12 13 12 13 3 12 13 17 36 As illustrated in, both the end portions in the vehicle width direction of the inner cross memberare attached to the side wall portionsandof the trayvia brackets. The inner cross memberis integrated with the side wall portionsandby the brackets. The vertical wall portion(both the vertical wall portionon the front side and the vertical wall portionon the rear side) and the side wall portionsandof the inner cross memberare connected by the brackets. The bracketsinclude the bracketon the left side that couples the left end portion in the vehicle width direction of the inner cross memberand the side wall portionand the bracketon the right side that couples the right end portion in the vehicle width direction of the inner cross memberand the side wall portion. Both the end portions in the vehicle width direction of the inner cross memberare inclined along the inner surface shapes (slope shapes) of the side wall portionsandand are in contact with the side wall portionsand. In this contact state, the inner cross memberis attached to the side wall portionsandby the brackets. Note that, in, the recessis omitted.

32 3 12 13 10 32 32 12 13 17 3 32 32 3 3 As a method of connecting the vertical wall portionof the inner cross memberand the side wall portionsandof the tray, both of the vertical wall portionon the front side and the vertical wall portionon the rear side are preferably connected to the side wall portionsandby the brackets. Accordingly, at the side surface collision of the electric vehicle, cross section collapse of the inner cross memberdue to the axis direction load less likely occurs and the axis direction load is dispersed and received by both of the vertical wall portionon the front side and the vertical wall portionon the rear side of the inner cross member. Therefore, the buckling of the inner cross membercan be suppressed.

32 32 3 12 13 10 17 17 With the CAE analysis explained above performed to check this point, as compared with when both of the vertical wall portionon the front side and the vertical wall portionon the rear side of the inner cross memberare connected to the side wall portionsandof the trayby the brackets, the maximum load (proof stress) of the load-stroke curve decreases by 26% when one of the bracketson the front side and the rear side is removed and the maximum load (proof stress) decreases by 62% when both of the brackets in the front side and the rear side are removed.

3 3 3 3 3 The proof stress of the inner cross memberis higher as the yield strength of a metal plate used for the inner cross memberis higher. For that reason, the inner cross memberis preferably formed from a steel sheet having a yield strength of 500 MPa class or more by roll forming or press forming. That is, the steel sheet forming the inner cross memberis preferably a steel sheet having tensile strength of 590 MPa class or more. The steel sheet forming the inner cross memberis more preferably a steel sheet having tensile strength of 980 MPa class or more and particularly preferably a steel sheet having tensile strength of 1180 MPa class or more.

7 FIG. 8 FIG. is a perspective view for explaining the structure of the side frame.is a cross-sectional view illustrating a cross-sectional shape of the side frame.

4 4 4 4 The side frameis configured by a structure made of steel sheet having a figure-eight cross section in which two rectangles are overlapped in the vehicle height direction. The side frameis formed by roll forming and has structure in which upper and lower quadrangular shapes are joined by continuous welding. The continuous welding includes welding methods such as arc welding and laser welding. The side frameis a structure including a plurality of ridgeline portions (bent portions) extending in the vehicle front-rear direction by repeating mountain fold and/or valley fold of the steel sheet. The side framehas a plurality of cross sections extending in the vehicle width direction.

4 51 52 53 54 55 56 57 58 59 60 61 62 63 The side frameincludes an upper surface portion, a side surface portionon the upper side, a side surface portionon the lower side, a lower surface portion, a first ridgeline portion, a second ridgeline portion, a third ridgeline portion, a fourth ridgeline portion, a fifth ridgeline portion, a sixth ridgeline portion, an intermediate surface portionin the center, an end portionon the upper side, and an end portionon the lower side.

51 51 52 55 52 53 54 54 53 56 The upper surface portionis a portion forming a first cross section extending in the vehicle width direction. The upper surface portionand the side surface portionare formed in series via the first ridgeline portion. The side surface portionon the upper side and the side surface portionon the lower side are wall portions extending in the vehicle height direction. The lower surface portionis a portion forming a second cross section extending in the vehicle width direction. The lower surface portionand the side surface portionare formed in series via the second ridgeline portion.

61 61 52 57 61 53 58 The intermediate surface portionis a portion forming a third cross section extending in the vehicle width direction. The intermediate surface portionand the side surface portionon the upper side are formed in series via the third ridgeline portion. The intermediate surface portionand the side surface portionon the lower side are formed in series via the fourth ridgeline portion.

62 61 62 52 59 4 59 58 4 58 59 62 61 52 61 59 52 61 59 58 59 The end portionon the upper side is a portion in contact with the upper surface of the intermediate surface portion. The end portionon the upper side and the side surface portionon the upper side are formed in series via the fifth ridgeline portion. In the side frame, the fifth ridgeline portionand the fourth ridgeline portionare joined by welding. The side framehas structure in which the fourth ridgeline portionand the fifth ridgeline portionare joined by a welded portion in a state in which the lower surface of the end portionand the upper surface of the intermediate surface portionare in surface contact. The side surface portionis provided continuously to the intermediate surface portionvia the fifth ridgeline portion. The side surface portionand the intermediate surface portionare integrated via the fifth ridgeline portionand the welded portion. The welded portion is provided to continuously or intermittently join the fourth ridgeline portionand the fifth ridgeline portionin the vehicle front-rear direction.

63 61 63 53 60 4 60 57 4 57 60 63 61 53 61 60 53 61 60 57 60 55 56 57 58 59 60 The end portionon the lower side is a portion in contact with the lower surface of the intermediate surface portion. The end portionon the lower side and the side surface portionon the lower side are formed in series via the sixth ridgeline portion. In the side frame, the sixth ridgeline portionand the third ridgeline portionare joined by welding. The side framehas structure in which the third ridgeline portionand the sixth ridgeline portionare joined by a welded portion in a state in which the upper surface of the end portionand the lower surface of the intermediate surface portionare in surface contact. The side surface portionis provided continuously to the intermediate surface portionvia the sixth ridgeline portion. The side surface portionand the intermediate surface portionare integrated via the sixth ridgeline portionand the welded portion. The welded portion is provided to continuously or intermittently join the third ridgeline portionand the sixth ridgeline portionin the vehicle front-rear direction. All of the first to sixth ridgeline portions,,,,, andare bent portions.

4 57 58 59 60 61 400 25 4 4 The side framehas structure in which four ridgeline portions including the third to sixth ridgeline portions,,, andand one cross section including the intermediate surface portionare added to a side frame (for example, a side frameillustrated in FIG.) having a simple quadrangular cross section as a whole. As explained above, in the structure made of the steel sheet in which the steel sheet is repeatedly mountain folded and/or valley folded, the plurality of ridgeline portions (bent portions) extending in the longitudinal direction (the vehicle front-rear direction) are formed in a mountain folded and/or valley folded portion and the plurality of cross sections extending in the direction orthogonal to the longitudinal direction (the vehicle width direction) and crossing or inclining in the vehicle width direction are formed, whereby the bending rigidity against the load (the side collision load) input from the direction orthogonal to the longitudinal direction of the side frame(the vehicle width direction) can be enhanced. For that reason, the side framehas high load-bearing performance (proof stress) even against a side collision load in the vehicle width direction.

4 4 4 4 The proof stress of the side frameis higher as the yield strength of the metal plate used for the side frameis higher. The side frameis desirably made of a steel sheet having higher yield strength compared with an aluminum alloy. This aluminum alloy is, for example, YS140 MPa of an Al—Si—Mg-based casting alloy. The steel sheet having the higher yield strength is, for example, a steel sheet YS420 MPa of having tensile strength of 590 MPa class. In particular, the side frameis desirably made of a steel sheet having tensile strength of 1180 MPa class or more.

1 4 1 100 4 51 54 61 4 10 12 FIG. In the battery case, the side framehas structure in which a plurality of ridgeline portions are formed in the vehicle front-rear direction by repeating mountain fold and/or valley fold of a steel sheet. Accordingly, it is possible to increase proof stress against a collision load input to the battery casethrough the side sill(illustrated in) at the time of side surface collision of the electric vehicle. Since the side framehas three cross sections including the upper surface portion, the lower surface portion, and the intermediate surface portion, it is possible to improve load-bearing performance against a load acting in the vehicle width direction at the time of side surface collision of the electric vehicle. In the side frame, an interval in the vehicle height direction between the cross sections extending in the vehicle width direction is set to half or less of the depth of the tray.

9 FIG. 10 FIG. 4 12 10 4 13 10 4 10 20 As illustrated in, the side frameis disposed at a position facing the outer surface of the side wall portionof the trayin the vehicle width direction. Similarly, the side frameis disposed at a position facing the outer surface of the side wall portionof the trayin the vehicle width direction. The side frameis connected to the trayvia a fixing member(see).

10 FIG. 11 FIG. 20 10 21 12 10 71 21 22 72 22 23 73 21 74 74 21 74 21 74 82 23 16 10 75 71 72 73 75 4 12 13 10 82 74 21 74 12 13 3 As illustrated in, the fixing memberis joined to the trayby welding. The first fixing memberis joined to the side wall portionof the trayby a welded portion. The first fixing memberand the second fixing memberare joined by a welded portion. The second fixing memberand the third fixing memberare joined by a welded portion. In the first fixing member, bolt positionsto which weld bolts are fixed are provided. The bolt positionsare portions that are located on the outer surface (a surface facing the vehicle width direction outer side) of the first fixing memberand to which head portions of the weld bolts are welded. At the bolt positions, the head portions of the weld bolts are fixed to the first fixing member. The weld bolts fixed to the bolt positionsis weld boltsexplained below. As illustrated in, the third fixing memberis joined to the bottomof the trayby a welded portion. All of the welded portion, the welded portion, the welded portion, and the welded portionare formed by spot welding. As explained below, the side frameis joined to the side wall portionsandof the trayvia the weld boltsfixed to the bolt positionsand the first fixing member. The bolt positionsare, in the side wall portionsand, outer surface sides of portions to which both the end portions in the vehicle width direction of the inner cross memberare attached.

20 21 22 23 72 73 20 10 71 75 20 100 1 100 20 1 100 20 20 1 The fixing memberhas structure in which the first fixing member, the second fixing member, and the third fixing memberare integrated by the welded portionsand. The fixing memberis integrated with the trayby the welded portionsand. Further, the fixing memberis attached to the side sillof the vehicle body structure by bolt fastening. For that reason, the battery caseis fixed to the side sillvia the fixing member. That is, the battery caseis supported by the side sillvia the fixing member. The fixing memberfunctions as a support member that supports the battery case.

1 1 100 1 10 2 The electric vehicle mounted with the battery caseneeds to have structure capable of withstanding a collision load input to the battery casethrough the side sillat the time of collision and protecting the battery in the battery case. The structure capable of protecting the battery is structure capable of preventing the tray(the main body) deformed by the collision load from coming into contact with the battery.

1 3 3 4 20 3 4 20 12 FIG. 14 FIG. 12 FIG. 2 FIG. 13 FIG. 2 FIG. 14 FIG. 2 FIG. Disposition examples at the time when the battery caseis mounted on the vehicle body are illustrated into. Note that, in, a cross-sectional view of a Y1 cross section illustrated inis illustrated. In, a cross-sectional view of a Y2 cross section illustrated inis illustrated. In, a cross-sectional view of a Y3 cross section illustrated inis illustrated. The Y1 cross section, the Y2 cross section, and the Y3 cross section are cross sections at different positions in the vehicle front-rear direction. The Y1 cross section is a cross section including a position where the inner cross memberis provided. The Y2 cross section is a cross section including a position where the inner cross memberis absent and a position where a fixing structure of the side frameand the fixing memberis provided. The Y3 cross section is a cross section including a position where the inner cross memberis absent and a position where the fixing structure of the side frameand the fixing memberis not provided.

12 FIG. 12 FIG. 1 120 100 120 100 120 121 121 120 100 121 100 1 120 120 11 100 1 100 17 As illustrated in, the battery caseis mounted under the floor of the vehicle body and is disposed below a floor paneland on the vehicle width direction inner side of the side sill. The floor panelis formed to spread between a pair of side sills. The floor panelis disposed below a floor cross member. The floor cross memberis provided on the upper surface of the floor panel, extends in the vehicle width direction, and extends over the pair of side sills. Both the end portions in the vehicle width direction of the floor cross memberare attached to the side sills. The battery caseis disposed below the floor panel. The lower surface of the floor paneland the upper surface of the coverface each other in the vehicle height direction. In vehicle side view, the side silland the battery caseare disposed at positions overlapping each other. The side sillis a member also called rocker in the vehicle body structure. In, the bracketsare omitted.

100 100 100 101 102 101 100 102 100 The side sillis an elongated vehicle body framework member extending in the vehicle front-rear direction and having a closed cross-sectional shape and a pair of left and right side sillsare provided on both the sides in the vehicle width direction. The side sillincludes an inner memberand an outer membermade of a press-molded material. The inner memberis a member configuring an inner side portion in the vehicle width direction of the side silland bulges to the inner side in the vehicle width direction and extends in the vehicle front-rear direction. The outer memberis a member configuring an outer side portion of the side sillin the vehicle width direction and bulges to the outer side in the vehicle width direction and extends in the vehicle front-rear direction.

101 102 101 102 101 102 100 101 102 100 100 100 101 102 12 FIG. 14 FIG. The inner memberis formed in a substantial hat shape in which a cross-sectional shape orthogonal to the vehicle front-rear direction directs an opening to the vehicle width direction outer side. The outer memberis formed in a substantial hat shape in which a cross-sectional shape orthogonal to the vehicle front-rear direction directs an opening to the vehicle width direction inner side. Upper portions of the inner memberand the outer memberare joined to each other and lower portions of the inner memberand the outer memberare joined to each other. Accordingly, the side sillhollow on the inside is configured. The inner memberand the outer memberare joined, whereby a closed cross-sectional shape is formed. Note that a stiffening structure for stiffening the side sillis provided on the inside of the side sill. Into, the internal structure of the side sillis omitted and only the outer shapes of the inner memberand the outer memberare illustrated.

12 FIG. 14 FIG. 12 FIG. 10 FIG. 12 FIG. 1 100 20 20 100 22 101 80 81 22 91 80 81 100 101 91 22 21 12 13 10 71 21 22 72 As illustrated into, the battery caseis fixed to the side sillvia the fixing member. As illustrated in, the fixing memberis fixed to the side sillby bolt fastening. The second fixing memberand a lower portion of the inner memberare fastened by a boltand a nut. As illustrated inand, in the second fixing member, a through holethrough which the boltis inserted is provided. The nutis, for example, a weld nut disposed inside the side silland welded to the inner surface of the inner member. The through holeis a hole formed to penetrate the second fixing memberin the vehicle height direction. The first fixing memberis joined to the outer surfaces of the side wall portionsandof the trayby the welded portion. The first fixing memberand the second fixing memberare joined by the welded portion.

13 FIG. 4 20 4 21 82 83 82 21 74 21 12 13 10 71 4 12 13 10 82 21 As illustrated in, the side frameis fixed to the fixing member. The side frameis fixed to the first fixing memberby weld boltsand nuts. The head portions of the weld boltsare joined to the first fixing memberat the bolt positions. Since the first fixing memberis joined to the outer surfaces of the side wall portionsandof the trayby the welded portion, the side frameis joined to the outer surfaces (surfaces facing the vehicle width direction outer side) of the side wall portionsandof the trayvia the weld boltsand the first fixing member.

4 52 53 12 13 52 53 12 13 52 52 61 57 52 61 59 53 53 61 58 53 61 60 52 53 12 13 82 21 61 4 52 53 61 58 59 52 53 12 13 4 4 7 FIG. 9 FIG. 7 FIG. 9 FIG. 13 FIG. In the side frame, the side surface portionsandare joined to the outer surfaces of the side wall portionsand. The side surface portionsandare portions joined to the outer surfaces of the side wall portionsand. As illustrated into, the side surface portionincludes the side surface portionon the outer side disposed relatively on the vehicle width direction outer side and formed in series with the intermediate surface portionvia the third ridgeline portionand the side surface portionon the inner side disposed relatively on the vehicle width direction inner side and provided continuously to the intermediate surface portionvia the fifth ridgeline portion. As illustrated into, the side surface portionincludes the side surface portionon the inner side disposed relatively on the vehicle width direction inner side and formed in series with the intermediate surface portionvia the fourth ridgeline portionand the side surface portionon the outer side disposed relatively on the vehicle width direction outer side and provided continuously to the intermediate surface portionvia the sixth ridgeline portion. As illustrated in, the side surface portionon the inner side and the side surface portionon the inner side are joined to the outer surfaces of the side wall portionsandvia the weld boltsand the first fixing member. The intermediate surface portionis a cross section transverse in the vehicle width direction or a cross section inclined with respect to the vehicle width direction. In the side frame, the side surface portionsandon the inner side are provided continuously to a cross section (the intermediate surface portion) crossing or inclined in the vehicle width direction via the bent portions (the fourth ridgeline portionand the fifth ridgeline portion). Since the side surface portionsandare joined to the outer surfaces of the side wall portionsand, the cross-sectional shape of the side frameis a cross-sectional shape in which bending rigidity against a load (a side collision load) input from a direction (the vehicle width direction) orthogonal to the longitudinal direction of the side frameis increased. Accordingly, collapse at the time of side surface collision can be suppressed and high collision resistance performance (proof stress) can be maintained even after the side surface collision.

82 52 4 53 4 83 4 82 83 4 51 4 10 4 20 The weld boltsinclude a first weld bolt penetrating the side surface portionof the side frameand a second weld bolt penetrating the side surface portionof the side frame. The nutsare attached to a side surface on the vehicle width direction outer side of the side frame. The weld boltsand the nutsmay be attached to the side framevia a collar. The upper surface of the upper surface portionof the side framemay be joined to the lower surface of the upper portion of the tray. As this joining method, spot welding, arc welding, adhesion by an adhesive, and the like are possible. When the side frameis fixed to the fixing memberusing bolts, the bolts are not limited to weld bolts, and stud bolts may be used.

14 FIG. 20 16 10 75 22 23 73 As illustrated in, the fixing memberis joined to the bottomof the trayby the welded portion. The second fixing memberand the third fixing memberare joined by the welded portion.

1 3 4 As explained above, according to the embodiment, it is possible to improve the collision performance of the battery casewhile suppressing an increase in weight by combining the cross-sectional shapes of the inner cross memberand the side framewith appropriate things.

1 The battery caseis not limited to the embodiment, and it is possible to configure a modification in which the shapes of the constituent members are different from those in the embodiment.

3 32 3 32 3 4 FIG. 15 FIG. For example, in the inner cross member, at least one ridgeline portion only has to be formed in the vertical wall portion. The inner cross memberis not limited to the structure in which the eight ridgeline portions are formed in the vertical wall portionas illustrated in. A modification of the inner cross memberis illustrated in.

15 FIG. 3 45 37 32 32 37 45 32 37 37 32 34 32 32 45 34 As illustrated in part a) of, the inner cross memberin the first modification has structure in which one ridgeline portionand one inclined wall portionare formed in one of the pair of vertical wall portions. In the vertical wall portion, the inclined wall portioninclined with respect to the vehicle height direction is formed. The ridgeline portionis a boundary portion between, in the vertical wall portion, a portion extending in the vehicle height direction and the inclined wall portion. The inclined wall portionis a wall portion formed between, in the vertical wall portion, a portion extending in the vehicle height direction and the upper bent section. The vertical wall portionextends to be inclined with respect to the vehicle height direction to approach the other vertical wall portionbetween the ridgeline portionand the upper bent section.

45 37 32 45 37 32 3 45 37 32 3 A set of the ridgeline portionand the inclined wall portionmay be provided in at least one of the pair of vertical wall portions. When a set of the ridgeline portionand the inclined wall portionis formed in only one of the pair of vertical wall portions, the number of ridgeline portions provided in the inner cross memberis one. When sets of the ridgeline portionand the inclined wall portionare formed in both of the pair of vertical wall portions, the number of ridgeline portions provided in the inner cross memberis two.

15 FIG. 3 46 47 38 32 38 32 32 46 32 38 47 38 32 32 As illustrated in part (b) of, the inner cross memberin the second modification has structure in which two ridgeline portionsandand an inclined wall portionare formed in one of the pair of vertical wall portions. The inclined wall portionis a wall portion formed between the vertical wall portionon the upper side and the vertical wall portionon the lower and extends to be inclined with respect to the vehicle height direction. The ridgeline portionon the upper side is a boundary portion between the vertical wall portionon the upper side and the inclined wall portion. The ridgeline portionon the lower side is a boundary portion between the inclined wall portionand the vertical wall portionon the lower. An interval between facing portions of the pair of vertical wall portionsis narrower in an upper side portion than in a lower side portion in the vehicle height direction.

46 47 38 32 46 47 38 32 3 46 47 38 32 3 A set of the two ridgeline portionsandand the inclined wall portionmay be provided in at least one of the pair of vertical wall portions. When the set of the two ridgeline portionsandand the inclined wall portionis formed in only one of the pair of vertical wall portions, the number of ridgeline portions provided in the inner cross memberis two. When sets of two ridgeline portionsandand the inclined wall portionare formed in both of the pair of vertical wall portions, the number of ridgeline portions provided in the inner cross memberis four.

15 FIG. 3 41 42 43 44 36 32 3 41 42 43 44 36 32 As illustrated in part (c) of, the inner cross memberin the third modification has structure in which four ridgeline portions,,, andand one recessare formed in only one of the pair of vertical wall portions. The inner cross memberhas structure in which a set of the four ridgeline portions,,, andand the recessis formed in only one of the pair of vertical wall portions.

15 FIG. 3 41 41 42 42 43 43 44 44 36 36 32 3 32 36 41 42 43 44 36 41 42 43 44 32 36 31 36 36 33 36 36 36 32 As illustrated in part (d) of, the inner cross memberin the fourth modification has structure in which eight ridgeline portionsA,B,A,B,A,B,A, andB and two recessesA andB are formed in only one of the pair of vertical wall portions. The inner cross memberhas structure in which two sets of four ridgeline portions and recesses are provided on only one of the pair of vertical wall portions. The recessA on the upper side is formed by the first ridgeline portionA on the upper side, the second ridgeline portionA on the upper side, the third ridgeline portionA on the upper side, and the fourth ridgeline portionA on the upper side. The recessB on the lower side is formed by the first ridgeline portionB on the lower side, the second ridgeline portionB on the lower side, the third ridgeline portionB on the lower side, and the fourth ridgeline portionB on the lower side. In the fourth modification, the one vertical wall portionincludes a portion where the recessA on the upper side is formed, a portion further on the top plate sectionside than the recessA on the upper side, a portion where the recessB on the lower side is formed, a portion further on the flange sectionside than the recessB on the lower side, and a portion between the recessA on the lower side and the recessB on the lower side. No ridgeline portion is formed in the other vertical wall portion.

3 12 13 10 17 A method of connecting the inner cross memberand the side wall portionsandof the trayis not limited to the attachment structure in which the bracketsare used and may be joining by welding.

16 FIG. 3 12 13 10 76 12 13 76 3 76 3 3 For example, as illustrated in, the vehicle width direction end portions of the inner cross memberare inclined along the inclined shapes of the side wall portionsandof the trayand are joined by a joining portionin a state of being in contact with the side wall portionsand. The joining portionis formed by continuous joining such as laser welding or arc welding. Since the vehicle width direction end portion of the inner cross memberis closed in a bag shape by the joining portion, cross section collapse of the inner cross membermuch less easily occurs. Accordingly, the proof stress of the inner cross membercan be further enhanced.

32 32 12 13 12 13 76 3 3 32 32 3 It is preferable that both of the vertical wall portionon the front side and the vertical wall portionon the rear side come into contact along the inner surface shape (the slope shape) of the side wall portionsandand are joined to the side wall portionsandby the joining portion. Accordingly, at the time of side surface collision of the electric vehicle, cross section collapse of the inner cross memberdue to an axis direction load less easily occurs and, in the inner cross member, the axis direction load is distributed and received by both of the vertical wall portionon the front side and the vertical wall portionon the rear side. Therefore, buckling of the inner cross membercan be suppressed.

3 3 3 17 FIG. The CAE analysis was performed in order to check proof stress by the structure of the inner cross member. As illustrated in, the inner cross membersset as a target of the CAE analysis are four types of inner cross membershaving structures of types A to D.

3 32 3 32 32 3 3 The inner cross memberof the type A is formed in a hat cross-sectional shape and a ridgeline portion is not provided in the vertical wall portion. In the structure of the type A, the number of ridgeline portions is zero. In contrast, in the inner cross membersof the types B, C, and D, at least one or more ridgeline portions are formed in the vertical wall portion. Note that ridgeline portions provided in the vertical wall portionsof the inner cross membersof the types B, C, and D are formed over the entire length in the longitudinal direction of the inner cross member.

3 32 32 45 32 The inner cross memberof the type B has structure in which one ridgeline portion is provided in the pair of vertical wall portions. In the structure of the type B, the number of ridgeline portions is one. In the structure of the type B, one part of the vertical wall portionon one side is bent to the outer side in a convex shape and the ridgeline portionis provided in only the vertical wall portionon one side.

3 32 41 42 43 44 32 The inner cross memberof the type C has structure in which four ridgeline portions are provided in the pair of vertical wall portions. In the structure of the type C, the number of ridgeline portions is four. In the structure of the type C, the ridgeline portions,,, andare provided in only the vertical wall portionon one side.

3 32 41 42 43 44 32 3 The inner cross memberof the type D has structure in which eight ridgeline portions are provided in the pair of vertical wall portions. In the structure of the type D, the number of ridgeline portions is eight. In the structure of the type D, the ridgeline portions,,, andare provided in each of both the vertical wall portions. Note that the inner cross membersof the types A to D are manufactured by roll forming.

18 FIG. 3 3 3 Then, for the structures of the types A to D, as illustrated in, the CAE analysis was performed in which one end on one side of the inner cross memberwas fixed and a load in the longitudinal direction (the vehicle width direction) was applied to the other end to deform the inner cross memberby 3 mm. This load is an axis direction load acting in the longitudinal direction of the inner cross member.

19 FIG. 3 is a diagram illustrating a correspondence relationship between a maximum load (proof stress) of a load-stroke curve obtained by the CAE analysis of the inner cross member and the number of ridgeline portions formed in the vertical wall portion of the inner cross member. Furthermore, Table 1 illustrates an example of a correspondence relationship between the maximum load of the load-stroke curve obtained by the CAE analysis and the number of ridgeline portions of the inner cross memberin the structures of the types A to D.

TABLE 1 Type A B C D Number of ridgeline portions 0 1 4 8 Weight (—) 1 0.95 1.01 1.01 Maximum load (kN) 51.7 51.7 84.9 120

3 The maximum load of the load-stroke curve is a load (proof stress) with which the inner cross memberstarts buckling deformation at the time of changing to plastic deformation through elastic deformation immediately after starting deformation and indicates proof stress against side surface collision. As the maximum load (proof stress) is higher, plastic deformation at the time of collision less easily occurs and collision characteristics are better.

19 FIG. 3 3 As illustrated in, the maximum load (proof stress) of the inner cross memberincreases substantially in proportion to the number of ridgeline portions. On the other hand, as illustrated in Table 1, in the structure of the type C and the structure of the type D, a weight increase with respect to the structure of the type A is also about 1% and it is possible to improve the rigidity of the inner cross memberwhile hardly increasing component weight from the structure of the hat cross-sectional shape of the type A. A numerical value of the weight illustrated in Table 1 is a numerical value representing a ratio based on the structure of type A.

3 36 32 36 36 32 3 3 36 36 36 32 32 36 17 FIG. In the inner cross memberof the type D, if the interval between the recessesof the facing vertical wall portionsis narrowed to be smaller than the interval illustrated in, mating surfaces can be brought into contact with each other and further joined. By bringing the facing recessesinto contact each other and joining the facing recesses, the vertical wall portionscan be prevented from being opened and buckled when a load is applied to the inner cross memberand a higher maximum load (proof stress) can be obtained. The maximum load of the load-stroke curve obtained by the CAE analysis of the inner cross memberof the type D is improved by 4% by bringing the facing recessesinto contact with each other and joining the facing recesses. A period (a stroke amount) in which a high load (for example, 100 kN or more) can be maintained even after the load-stroke curve reaches the maximum load is improved to 2.3 times by bringing the recessesof the facing vertical wall portionsinto contact with each other and improved to 4.0 times by bringing the recesses of the facing vertical wall portionsinto contact with each other and joining the recesses. As a method of joining the recesses, spot welding, arc welding, adhesion using an adhesive, and the like are possible.

3 12 13 10 3 3 1 2 3 4 17 FIG. The CAE analysis was performed on the method of connecting the inner cross memberand the side wall portionsandof the trayin order to check proof stress due to a difference in a connection method. The inner cross memberset as a target of the CAE analysis is the inner cross memberhaving the structure of type D illustrated in. As the difference in the connection method, a condition, a condition, a condition, and a conditionwere provided.

1 32 32 12 13 12 13 76 16 FIG. The conditionis a connection method in which, as illustrated in, both of the vertical wall portionon the front side and the vertical wall portionon the rear side come into contact along the inner surface shapes of the side wall portionsand(slope shapes in which the upper side of the side wall portions is inclined to the vehicle width direction outer side) and are joined to the side wall portionsandby joining portions.

2 32 32 12 13 12 13 76 1 The conditionis a connection method in which both the vertical wall portionon the front side and the vertical wall portionon the rear side are in contact along the inner surface shapes of the side wall portionsandbut are not joined to the side wall portionsand. When the joining portionis removed from the connection method of the condition, the connection method of the second condition is obtained.

3 32 12 13 12 13 32 12 13 The conditionis a connection method in which only the vertical wall portionon the front side comes into contact along the inner surface shapes of the side wall portionsandand is joined to the side wall portionsand. In this case, the end portion of the vertical wall portionon the rear side is rectangular and is neither in contact with nor joined to the inner surface shapes of the side wall portionsand.

4 32 32 12 13 The conditionis a connection method in which the end portions of both of the vertical wall portionon the front side and the vertical wall portionon the rear side are rectangular and are neither in contact with nor joined to the inner surface shapes of the side wall portionsand.

38 FIG. 39 FIG. 3 3 300 12 13 10 12 13 1 4 3 300 3 300 Then, as illustrated in, one end of one side of the inner cross memberwas fixed (not illustrated), a relationship between the other end of the inner cross member, a rigid wallin which the inner surface shapes of the side wall portionsandof the trayare simulated and the upper side of the side wall portionsandis inclined 2 degrees to the vehicle width direction outer side was set as structure for the conditionsto, and the CAE analysis of deforming the inner cross memberby 3 mm by applying a load in the vehicle width direction to the rigid wall. In this CAE analysis, an axis direction load acts in the longitudinal direction of the inner cross membervia the rigid wall. The results of the CAE analysis are illustrated in.

39 FIG. 1 32 32 12 13 12 13 76 3 1 As illustrated in, in the conditionin which both of the vertical wall portionon the front side and the vertical wall portionon the rear side are in contact along the inner surface shapes (the slope shapes) of the side wall portionsandand are joined to the side wall portionsandby the joining portions, the maximum load (proof stress) of the inner cross membercan be maximized. In the connection method of the condition, the maximum load is 120 kN.

76 1 2 3 12 13 1 3 3 12 13 1 4 3 12 13 76 3 12 13 3 12 13 39 FIG. When the joining portionis removed from the condition, the maximum load decreases by 12% (the condition). In the connection method of the second condition, the maximum load is 106 kN. If the inner cross memberand the side wall portionsandare brought into contact with each other and joined only to the vertical wall portion on the front side with respect to the condition, the maximum load decreases by 27% (the condition). In the connection method of the third condition, the maximum load is 88 kN. If the inner cross memberand the side wall portionsandare not brought into contact and joined with respect to the condition, the maximum load decreases by 63% (the condition). In the connection method of the fourth condition, the maximum load is 45 kN. Note that black circles illustrated inindicate that the inner cross memberis in contact along the inner surface shapes of the side wall portionsandand is joined by the joining portion. White circles indicate that the inner cross memberis in contact along the inner surface shapes of the side wall portionsandbut is not joined. Cross marks indicate that the inner cross memberis neither in contact along the inner surface shapes of the side wall portionsandnor joined.

4 4 20 FIG. 22 FIG. The structure of the side frameis not limited to a structure having a figure-eight cross section in which two rectangles are overlapped in the vehicle height direction. Modifications of the side frameare illustrated into.

20 FIG. 4 130 150 130 130 150 As illustrated in, the side framein a first modification includes a first membermade of steel having a W-shaped cross section spreading to the outer side in the vehicle width direction and a second memberhaving a flat shape disposed on the vehicle width direction outer side of the first member. The first memberand the second memberare joined by welding.

130 131 132 133 134 135 136 137 138 139 140 141 142 143 The first memberincludes an upper surface portion, a first bent portion, a side surface portion, a first ridgeline portion, an inclined surface portion, a second ridgeline portion, a side surface portion, a third ridgeline portion, an inclined surface portion, a fourth ridgeline portion, a side surface portion, a second bent section, and a lower surface portion.

131 132 131 133 133 134 133 135 135 133 137 135 136 135 137 137 133 138 137 139 139 137 141 139 140 139 141 141 133 141 137 142 141 143 143 130 131 135 139 143 The upper surface portionis a portion forming a first cross section extending in the vehicle width direction. The first bent portionis a bent portion connecting the upper surface portionand the side surface portion. The side surface portionis a wall portion extending in the vehicle height direction on the vehicle width direction inner side. The first ridgeline portionis a boundary portion between the side surface portionand the inclined surface portion. The inclined surface portionis a wall portion formed between the side surface portionand the side surface portionand is inclined with respect to the vehicle height direction. The inclined surface portionis a portion forming a second cross section extending in the vehicle width direction. The second ridgeline portionis a boundary portion between the inclined surface portionand the side surface portion. The side surface portionextends in the vehicle height direction further on the vehicle width direction outer side than the side surface portion. The third ridgeline portionis a boundary portion between the side surface portionand the inclined surface portion. The inclined surface portionis a wall portion formed between the side surface portionand the side surface portionand is inclined with respect to the vehicle height direction. The inclined surface portionis a portion forming a third cross section extending in the vehicle width direction. The fourth ridgeline portionis a boundary portion between the inclined surface portionand the side surface portion. The side surface portionis a wall portion extending in the vehicle height direction below the side surface portion. The side surface portionis provided further on the vehicle width direction inner side than the side surface portion. The second bent sectionis a bent portion connecting the side surface portionand the lower surface portion. The lower surface portionis a portion forming a fourth cross section extending in the vehicle width direction. As explained above, the cross section of the first memberincludes four cross sections including the upper surface portion, the inclined surface portion, the inclined surface portion, and the lower surface portion.

130 4 134 136 138 140 135 139 400 4 25 FIG. The first memberhaving a W-shaped cross section is manufactured by press forming or roll forming. The side framehas structure in which four ridgeline portions,,,and two cross sections including inclined surface portionsandare added to a side frame (the side frameillustrated in) having a simple quadrangular cross section. For that reason, the side frameof the first modification has high load-bearing performance.

130 150 151 151 150 4 151 4 20 FIG. The first membermade of a steel sheet and the second memberhaving the flat shape are integrated by butt joining in a joining portion. The joining portionis a joining portion formed by butting and joining the vehicle height direction both end portions of the second memberhaving the flat shape. In the side framein the first modification, in a portion surrounded by a broken line circle in, a joining portionby laser welding is formed for the purpose of setting the radius of the corner portion zero. Accordingly, desired load-bearing performance in the side framecan be obtained.

130 4 150 137 130 130 150 151 4 150 4 The first memberhas a W-shaped cross section spreading to the vehicle width direction outer side. A part on the vehicle width direction outer side in the side frameneeds to have proof stress against a pressing force (a compression load) input from the outside at the time of side collision. Therefore, the second memberhaving the flat shape was disposed further on the vehicle width direction outer side of the side surface portionof the first memberand the first memberand the second memberwere joined by the joining portion. For that reason, in the side frameof the first modification, the second memberforms a side surface facing the vehicle width direction outer side (the surface on the vehicle width direction outer side of the side frame).

150 137 130 152 152 130 150 152 Furthermore, the center in the vehicle height direction of the second membermay be joined to the side surface portionof the first memberby a joining portion. The joining portionis a joining portion formed by spot welding or laser welding. Accordingly, the load-bearing performance can be improved by approximately 10%. A load bearing capacity increases because, by being joined, a maximum compression stress generation portion at the time of bending deformation becomes a double sheet joining portion formed by combining two steel sheets. The first memberand the second membermay not be joined at the center in the vehicle height direction. That is, the joining portionmay not be always provided.

21 FIG. 4 160 170 160 As illustrated in, the side framein the second modification includes a first membermade of a steel sheet having a hat cross-sectional shape spreading toward the inner side in the vehicle width direction and a second memberhaving a U-shaped cross section disposed to cover the vehicle width direction outside of the first member.

160 161 162 163 164 165 The first memberhaving the hat cross-sectional shape includes a side surface portion, an inclined surface portion, a side surface portion, an inclined surface portion, and a side surface portion.

161 4 162 163 161 165 164 165 4 161 The side surface portionon the upper side is a portion forming a side surface on the vehicle width direction inner side of the side frameand extends in the vehicle height direction. The inclined surface portionon the upper side is a portion that is inclined with respect to the vehicle height direction and forms a first cross section extending in the vehicle width direction. The side surface portionin the center is formed further on the vehicle width direction outer side than the side surface portionsand. The inclined surface portionon the lower side is a portion that is inclined with respect to the vehicle height direction and forms a second cross section extending in the vehicle width direction. The side surface portionon the lower side is a portion forming a side surface on the vehicle width direction inner side of the side frameand extends in the vehicle height direction below the side surface portion.

170 171 172 173 174 175 The second memberhaving the U-shaped cross section includes an upper surface portion, a punch shoulder R portionon the upper side, a side surface portion, a punch shoulder R portionon the lower side, and a lower surface portion.

171 172 171 173 173 160 173 4 174 173 175 175 The upper surface portionis a portion forming a third cross section extending in the vehicle width direction. The punch shoulder R portionis a bent portion connecting the upper surface portionand the side surface portion. The side surface portionis disposed further on the vehicle width direction outer side than the first memberand extends in the vehicle height direction. The side surface portionis a portion forming a side surface on the vehicle width direction outer side of the side frame. The punch shoulder R portionon the lower side is a bent portion connecting the side surface portionand the lower surface portion. The lower surface portionis a portion forming a fourth cross section extending in the vehicle width direction.

4 172 174 170 170 In the side framein the second modification, a relationship between a curvature radius R of the punch shoulder R portionsandof the second memberand a plate thickness t of the second memberpreferably satisfies R/t≤3.0.

160 170 161 171 165 175 170 163 160 The vehicle height direction both end portions of the first memberare joined to the second memberby welding or the like. The upper end of the side surface portionon the upper side is joined to the lower surface of the upper surface portion. The lower end of the side surface portionon the lower side is joined to the upper surface of the lower surface portion. As this joining method, spot welding, arc welding, adhesion by an adhesive, and the like are possible. The center in the vehicle height direction of the second membermay be joined to the side surface portionof the first memberby a joining portion formed by spot welding or laser welding.

160 170 160 170 171 161 175 165 21 FIG. 22 FIG. 22 FIG. A method of joining the first memberand the second memberis not limited to the example illustrated in. For example, the first memberand the second membercan be joined as illustrated in. In an example illustrated in, the end portion on the vehicle width direction inner side of the upper surface portionis joined to the surface on the vehicle width direction outer side of the side surface portionand the end portion on the vehicle width direction inner side of the lower surface portionis joined to the surface on the vehicle width direction outer side of the side surface portion. As this joining method as well, spot welding, arc welding, adhesion by an adhesive, and the like are possible.

4 200 4 3 4 200 400 23 FIG. 24 FIG. 25 FIG. The CAE analysis was performed in order to check the load-bearing performance due to the structure of the side frame. In this CAE analysis, as illustrated in, a load simulating side surface collision by the polewas applied from both support points to the center in a state in which both ends of the side framewere supported. An interval between two support points is an interval in the vehicle front-rear direction in which the inner cross memberis disposed. Alternatively, the interval between the two support points is the width in the vehicle front-rear direction of the battery. Then, as illustrated in, the CAE analysis for deform the side frameby 15 mm by causing the polesto project sideways was performed. As illustrated in, the side framehaving the simple quadrangular cross section was used as a side frame in a comparative example.

26 FIG. 26 FIG. 4 is a diagram illustrating a maximum load (proof stress) of a load-stroke curve obtained by the CAE analysis.illustrates a result obtained by verifying, with the CAE analysis, load-bearing performance against a load acting in the vehicle width direction at the time of side surface collision of the side frames. The side frames set as targets of the CAE analysis are four types of side frames having structures of types E to H.

20 FIG. 20 FIG. 21 FIG. 25 FIG. 4 152 152 4 4 400 As illustrated in, the side frame of the type H has structure in the case in which the side framein the first modification includes the joining portion. As illustrated in, the side frame of the type F has structure in the case in which the joining portionis absent in the side framein the first modification. As illustrated in, the side frame of the type G is the side framein the second modification. As illustrated in, the side frame of type E is the side framehaving the simple quadrangular cross section.

26 FIG. As illustrated in, it was confirmed that the structures of the types E, F, and G showed a maximum load (proof stress) higher by 42% to 107% than that of the structure of the type H and had high load-bearing performance.

27 FIG. 23 FIG. 24 FIG. is a diagram illustrating a relationship between the load-bearing performance of the side frame at the time of side surface collision obtained by the CAE analysis illustrated inand, the curvature radius of the punch shoulder R portion of the second member having the U-shaped cross section, and the plate thickness of the second member.

172 174 170 170 4 130 150 151 4 4 27 FIG. 20 FIG. 27 FIG. In a relationship between the curvature radius R of the punch shoulder R portionsandof the second memberand the plate thickness t of the second member, as illustrated in, as R/t decreases, the load-bearing performance against a load acting in the vehicle width direction at the time of side surface collision is improved. When R/t is 0, the load-bearing performance can be improved most. Note that, about the structure of the side framein the first modification illustrated in, a structure in which the first memberand the second memberare butted and joined (a structure including the joining portion) is one of forms in the case in which R/t illustrated inis 0. Since the side framein the first modification has R/t of 0, the side framehas high load-bearing performance.

A reason why the load-bearing performance is improved as R/t decreases in the relationship between the curvature radius R and the plate thickness t can be described as follows.

4 4 173 170 172 174 170 171 175 170 172 174 170 In a pole side surface collision mode, when a load is input to the side frame, when being considered in a cross section perpendicular to the vehicle front-rear direction passing through a pole center portion, a side surface portion on the vehicle width direction outer side of the side frame(the side surface portionof the second memberhaving the U-shaped cross section) is in a bending deformed state in which the side surface portion is on a compression side. At this time, when the curvature radius R (that is, R/t) of the punch shoulder R portionsandof the second memberis large, buckling deformation in which the upper surface portionand the lower surface portionof the second memberhaving the U-shaped cross section respectively collapse to the outer side to spread in the vehicle height direction easily occurs at the time of side surface collision. In contrast, when the curvature radius R (that is, R/t) of the punch shoulder R portionsandof the second memberhaving the U-shaped cross section is reduced, this buckling deformation less easily occurs. For that reason, proof stress against a collision load is improved. In particular, when R/t≤3.0, the maximum load (proof stress) at the time of side surface collision increases, which is preferable as structure.

28 FIG. 1 6 2 10 6 14 15 6 10 As illustrated in, as a modification of the battery case, a center framecan be disposed on the inside of the main body. In the tray, the center frameis disposed at the center in the vehicle width direction, extends in the vehicle front-rear direction, and extends over the front wall portionand the rear wall portion. The center framecan divide the inside of the trayinto two in the vehicle width direction.

3 12 13 6 3 3 12 6 3 13 6 3 6 6 3 One end in the vehicle width direction of the inner cross memberis attached to the side wall portionor the side wall portionand the other end in the vehicle width direction thereof is attached to the center frame. The inner cross memberincludes an inner cross memberA on the left side provided to extend over the left side wall portionand the center frameand an inner cross memberB on the right side provided to extend over the right-side wall portionand the center frame. An attachment structure for the inner cross memberand the center framemay be a fixing method in which a fixing member such as a bracket is used or a joining method by welding or adhesion. In this modification, by providing the center frame, the buckling wave length in the vehicle width direction of the inner cross membercan be reduced and the maximum load (proof stress) at the time of side surface collision can be increased.

29 FIG. 18 16 10 1 10 16 18 10 16 10 As illustrated in, uneven portionshaving an uneven shape may be formed in a mounting portion of battery cells in the bottomof the trayof the battery case. The traywas formed into a deep drawn molded product made of steel and an uneven shape to be a pipe shape was formed on the bottomat the same time by bulging. The uneven portionscan improve surface rigidity of the tray, suppress oil scanning of the bottom, and improve rigidity of the tray.

29 FIG. 16 18 19 92 1 19 92 19 16 1 16 10 Further, as illustrated in, the bottomon which the uneven portionsare formed may be covered with a flat panelor the like and sealed to form a flow paththrough which a coolant for cooling the battery cells flows. The battery caseincludes the flat panelfor confining the coolant in the flow path. The flat panelis joined to the bottomby laser welding, brazing, or the like. Then, it is possible to configure a form of the battery casein which an uneven shape to be a cooling pipe is imparted to the bottomof the tray.

92 10 19 16 18 16 92 10 19 10 30 FIG. The flow pathcan be formed in a protruding shape in the inward direction of the trayand can be formed in structure to be sealed by the flat panelfrom the lower side of the bottom surface of the bottom. Alternatively, as illustrated in, the uneven portionsmay be formed in a convex shape downward in the vehicle height direction from the bottom. In this case, the flow pathin which the coolant passes may be formed a protruding shape to the outward direction of the trayand may be formed in a seal structure in which the flat panelis set on the inside of the tray.

<Interval in the Vehicle Front-Rear Direction in which Inner Cross Member is Disposed>

40 FIG. 23 FIG. 8 FIG. 40 FIG. 3 4 200 51 61 61 54 3 4 4 200 Part (a) ofillustrates a diagram in which, in the CAE analysis illustrated in, at the time when the interval (the width in the vehicle front-rear direction of the battery, simply referred to as span) in the vehicle front-rear direction in which the inner cross memberis disposed, a dimension ratio (b/H) and the plate thickness t of the side framehaving the cross-sectional shape illustrated inare changed, and a load simulating side surface collision by the poleis applied from both support points to the center, a load (proof stress) at a reference punch intrusion amount is evaluated as an evaluation load. In parts (a) and (b) of, b denotes width and H denotes an interval between the upper surface portionand the intermediate surface portionand an interval between the intermediate surface portionand the lower surface portion. Then, suitable design ranges of the span, the dimension ratio (b/H), and the plate thickness t of the inner cross memberwere determined. As the dimension ratio (b/H) is smaller (the bending rigidity of the side frameis smaller) and the span is longer, the side frameis flexurally deformed by side surface collision by the poles. Therefore, the evaluation load decreases.

4 3 4 3 40 FIG. 2 In order to obtain a desired evaluation load (for example, 9 kN/kg or more), it is preferable to properly set the dimension ratio (b/H) and the plate thickness t of the side framewith respect to the interval (the span) in the vehicle front-rear direction in which the inner cross memberis disposed. For example, in the example illustrated in part (a) of, when the yield strength of 850 MPa is used, the dimension ratio (b/H) of the side framesis preferably set to b/H<2.3 and a relationship of (the span of the inner cross member)≤279×(b/H)×t+110 is preferably satisfied.

100 121 14 1 12 13 5 10 400 1 31 FIG. 31 FIG. In order to check the effect of the battery case structure in the present disclosure, the battery case, the floor cross member, and the side sill were modeled, and the CAE analysis at the time when the pole collided with the side surface of the battery case was performed. A model used in the CAE analysis is a half model symmetrical at the center in the vehicle width direction. For this half model, the center in the vehicle width direction was fixed with a rigid wall, the rigid wall was completely restrained, and the pole was caused to collide with the side surface of the side sill. The radius of the pole is 127 mm and initial speed is 30.9 km/h. The pole was caused to collide with the side sillin the vehicle width direction at a position where the center position of the pole overlaps the center position in the vehicle front and rear direction of the floor cross member. The center position in the vehicle front-rear direction is, for example, a cross section taken along a plane orthogonal to the vehicle front-rear direction at a position of 785 mm rearward from the front surface of the front wall portionof the battery case. Then, an evaluation distance was evaluated when a pole penetration amount was 102 mm after the pole came into contact with the side surface of the side sill. As illustrated in, the evaluation distance is a minimum distance between the side wall portionsandand the batteryon the inside of the trayat the time of side surface collision. The longer evaluation distance indicates that collision characteristics are more satisfactory. Note that the side frameillustrated inis a side frame in a comparative example.

32 FIG. 33 FIG. 32 FIG. is a diagram illustrating a disclosure example set as a target of the CAE analysis and a comparative example.is a graph illustrating CAE analysis results in the disclosure example and the comparative example. Note that, in, a combination of an inner cross member and a side frame is illustrated as a framework structure.

32 FIG. 4 FIG. 20 FIG. 32 FIG. 33 FIG. 1 1 1 3 1 4 1 As illustrated in, the framework structure of a disclosure exampleis a structure in which an inner cross member having eight ridgeline portions in vertical wall portions and a side frame including a structure made of a steel sheet having a W-shaped cross section spreading to the outer side in the vehicle width direction are combined. In the inner cross member in the disclosure example, a recess is formed at a center position in the vehicle height direction in each of a pair of vertical wall portions and eight ridgeline portions in total are provided. The inner cross member in the disclosure examplehas the same structure as the inner cross memberillustrated in. The side frame in the disclosure examplehas the same structure as the side frameillustrated in. In a result of the CAE analysis in the disclosure example, as illustrated inand, the minimum distance (the evaluation distance) between the side wall portion of the tray and the battery at the time when an intrusion amount of the pole reached 102 mm was 4.2 mm.

32 FIG. 21 FIG. 32 FIG. 33 FIG. 2 2 1 2 4 172 174 170 2 As illustrated in, a framework structure in a disclosure exampleis a structure in which an inner cross member having eight ridgeline portions in vertical wall portions and a side frame including a structure made of steel sheet having a hat cross-sectional shape spreading toward the inner side in the vehicle width direction are combined. The inner cross member in the disclosure examplehas the same structure as the inner cross member in the disclosure example. The side frame in the disclosure examplehas the same structure as the side frameillustrated in. The curvature radius of the punch shoulder R portionsandof the second memberis R=2.4 mm, the plate thickness is t=1.2 mm, and R/t=2.0 (≤3.0) is satisfied. In a result of the CAE analysis in the disclosure example, as illustrated inand, the minimum distance (the evaluation distance) between the side wall portion of the tray and the battery at the time when the penetration amount of the pole reached 102 mm was 3.9 mm.

32 FIG. 8 FIG. 32 FIG. 33 FIG. 34 FIG. 3 3 1 4 3 3 As illustrated in, a framework structure of in a disclosure exampleis a structure in which an inner cross member having eight ridgeline portions in vertical wall portions and a side frame including a structure made of a steel sheet having a figure-eight cross section in which two rectangles are overlapped in the vehicle height direction are combined. The inner cross member in the disclosure examplehas the same structure as the inner cross member in the disclosure example. The side frame of the third disclosure has the same structure as the side frameillustrated in. In a result of the CAE analysis in the disclosure example, as illustrated inand, the minimum distance (the evaluation distance) between the side wall portion of the tray and the battery at the time when the penetration amount of the pole reached 102 mm was 4.5 mm. A deformed state at this time is as illustrated in part (a) of. In the disclosure example, when the penetration amount of the pole reaches 102 mm, a gap remains between the side wall portion of the tray and the vehicle width direction end portion of the battery and the side wall and the battery are not in contact.

32 FIG. 20 FIG. 32 FIG. 33 FIG. 34 FIG. 4 4 1 4 1 4 4 4 As illustrated in, the framework structure of a disclosure exampleis a structure in which an inner cross member having eight ridgeline portions in vertical wall portions and a side frame including a structure made of a steel sheet having a W-shaped cross section spreading to the outer side in a vehicle width direction. The inner cross member in the disclosure examplehas the same structure as the inner cross member in the disclosure example. In the side frame in the disclosure example, the side frame in the disclosure example(the side frameillustrated in) is reversed in the vehicle width direction and two protrusions of the W-shaped cross section are disposed toward the vehicle width direction outer side. In a result of CAE analysis in the disclosure example, as illustrated inand, the minimum distance (the evaluation distance) between the side wall portion of the tray and the battery at the time when the penetration amount of the pole reached 102 mm was 3.8 mm. A deformed state at this time is as illustrated in part (b) of. In the disclosure example, when the intrusion amount of the pole reaches 102 mm, a gap remains between the side wall portion of the tray and the vehicle width direction end portion of the battery, and the side wall and the battery are not in contact with each other.

1 4 1 4 In all of the inner cross members in the disclosure examplesto, the flange section is joined to the bottom of the tray of the battery case by spot welding and the vehicle width direction end portion of the inner cross member is attached to the side wall portion of the tray via the bracket in a state in which the vehicle width direction end portion is in contact with and along the side wall portion of the tray. In all of the side frames in the disclosure examplesto, an interval in the vehicle height direction between the cross sections extending in the vehicle width direction is set to half or less of the depth of the tray.

32 FIG. 17 FIG. 25 FIG. 32 FIG. 33 FIG. 35 FIG. 1 1 3 1 1 1 400 1 1 1 3 As illustrated in, a framework structure in the comparative exampleis a structure in which an inner cross member having a hat cross-sectional shape in which a ridgeline portion is not provided in a vertical wall portion and a side frame having a simple quadrangular cross section are combined. The inner cross member in the comparative examplehas the same structure as the structure of the inner cross memberof the type A illustrated in. In the side frame in the comparative example, unlike the side frame in the disclosure example, a ridgeline portion along the vehicle front-rear direction is not formed in the vertical wall portions. The side frame in the comparative examplehas the same structure as the side frameillustrated in. In a result of the CAE analysis in the comparative example, as illustrated inand, the minimum distance (the evaluation distance) between the side wall portion of the tray and the battery at the time when the penetration amount of the pole reached 102 mm was 2.5 mm. A deformed state at this time is as illustrated in part (a) of. In the comparative example, when the intrusion amount of the poles reaches 102 mm, a gap remains between the side wall portion of the tray and the battery and the side wall is not in contact with the vehicle width direction end portion of the battery. When the comparative exampleis compared with the disclosure example, the side frame is greatly deformed and crushed and the inner member and the fixing member of the side sill are greatly distorted.

32 FIG. 32 FIG. 33 FIG. 2 2 1 2 1 2 As illustrated in, a framework structure of a comparative exampleis a structure in which an inner cross member having eight ridgeline portions in the vertical wall portions and a side frame having a simple quadrangular cross section are combined. The inner cross member in the comparative examplehas the same structure as the structure of the inner cross member in the disclosure example. The side frame in the comparative examplehas the same structure as the structure of the side frame in the comparative example. In a result of the CAE analysis in the comparative example, as illustrated inand, the minimum distance between the side wall portion of the tray and the battery at the time when the penetration amount of the poles reached 102 mm was 3.2 mm.

32 FIG. 32 FIG. 33 FIG. 3 3 1 3 3 3 As illustrated in, a framework structure in a comparative exampleis a structure in which an inner cross member having a hat cross-sectional shape in which a ridgeline portion is not provided in a vertical wall portion and a side frame including a steel sheet structure having a figure-eight cross section in which two rectangles are overlapped in the vehicle height direction are combined. The inner cross member in the comparative examplehas the same structure as the structure of the inner cross member in the disclosure example. The side frame in the comparative examplehas the same structure as the structure of the side frame in the disclosure example. In a result of the CAE analysis in the comparative example, as illustrated inand, the minimum distance (the evaluation distance) between the side wall portion of the tray and the battery at the time when the penetration amount of the poles reached 102 mm was 3.1 mm.

1 4 1 4 1 4 1 3 4 4 4 33 FIG. 35 FIG. As in the comparative example, a framework structure in a comparative exampleis a structure in which an inner cross member having a hat cross-sectional shape in which a ridgeline portion is not provided in a vertical wall portion and a side frame having a simple quadrangular cross section are combined. Unlike in the comparative example, in a comparative example, the vehicle width direction end portion of the inner cross member is not attached to the side wall portion of the tray. In contrast, in both of the disclosure examplestoand the comparative examplesto, the vehicle width direction end portion of the inner cross member is attached to the side wall via the bracket in a state in which the vehicle width direction end portion of the inner cross member is in contact along the side wall portion of the tray. In a result of the CAE analysis in the comparative example, as illustrated in, the minimum distance (the evaluation distance) between the side wall portion of the tray and the battery at the time when the penetration amount of the poles reached 102 mm was-25 mm. In a deformed state in the comparative example, as illustrated in part (b) of, the side wall portion of the tray was in contact with the vehicle width direction end portion of the battery when the intrusion amount of the poles reached 77 mm. For that reason, the evaluation distance in the comparative exampleis-25 mm (=77 mm-102 mm).

1 4 1 3 4 In all of the inner cross members in the comparative examplesto, the flange section is joined to the bottom of the tray of the battery case by spot welding. In the comparative examplesto, the vehicle width direction end portion of the inner cross member is attached to the side wall portion of the tray via the bracket. On the other hand, in only the inner cross member in the comparative example, the vehicle width direction end portion is not attached to the side wall portion of the tray.

33 FIG. 1 4 1 1 2 1 3 3 2 3 3 2 3 As illustrated in, in the disclosure examplesto, the evaluation distance is 1.4 mm to 2.0 mm longer than that in the comparative exampleand the collision characteristics are improved. When the comparative exampleand the comparative exampleare compared, the evaluation distance was improved by 0.7 mm by changing to a cross-sectional form to a cross-sectional form in which ridgeline portions extending in the vehicle width direction are provided on the vertical wall portions on both the sides of the inner cross member. When the comparative exampleand the comparative exampleare compared, the evaluation distance was improved by 0.6 mm by providing a plurality of ridgeline portions (bent portions) in the vehicle front-rear direction of the side frame and a plurality of cross sections extending in the vehicle width direction. The framework structure in the disclosure exampleis a combination of the inner cross member in the comparative exampleand the side frame in the comparative example. With the CAE analysis result in the disclosure example, because of an synergistic effect of the above, a collision characteristic improvement margin of 2.0 mm (=4.5 mm-2.5 mm) larger than a total improvement margin of 1.3 mm (=0.7 mm+0.6 mm) in the comparative exampleand the comparative examplewas obtained.

From the above, it has been demonstrated that it is possible to improve the collision performance of the battery case while suppressing an increase in weight by combining the cross-sectional shapes of the inner cross member and the side frame with appropriate one by the disclosure examples.

According to the present disclosure, it is possible to achieve a structure of a battery case having rigidity and strength higher than those in the related art without requiring a significant increase in weight and manufacturing cost.

1 BATTERY CASE 2 MAIN BODY 3 INNER CROSS MEMBER 4 SIDE FRAME 10 TRAY 11 COVER 12 13 ,SIDE WALL PORTION 14 FRONT WALL PORTION 15 REAR WALL PORTION 20 FIXING MEMBER 21 FIRST FIXING MEMBER 22 SECOND FIXING MEMBER 23 THIRD FIXING MEMBER 31 TOP PLATE SECTION 32 VERTICAL WALL PORTION 33 FLANGE SECTION 34 UPPER BENT SECTION 35 LOWER BENT SECTION 36 RECESS 41 42 43 44 45 46 47 ,,,,,,RIDGELINE PORTION 172 174 ,PUNCH SHOULDER R PORTION